I used the write function to write some stuff into a file. now i want to insert a blank link into the file before the next write function, do anyone know how to do that?
Write(logs,log,strlen(log));
is my first write, so now is the new line going to be:
Write(logs,'/n',strlen(log));
or should I create a new char[3] = '/n';
?
Assuming that you mean the POSIX write()
function, something like this should work:
write(logs,"\n",1);
Note that "\\n"
is a 1 character string - you may want "\\r\\n"
depending on if you need a carriage return and a new line in the file.
I know this post is pretty old but, I'am creating a log file and when I attempt to write a "\\n" it won't write it....:
write(fd,"\\n\\n==== NEW CLIENT ====\\n\\n",24);
The output in the file is:
==== NEW CLIENT ====
Without any blank line...any idea ? even if I put:
write(fd,"\\n",1);
nothing to do... :/
I got it...i was compiling the program in linux and checking the log file in windows, if I open the log file in linux it's ok...
The first problem that you need to address is that the newline character is represented by backslash-n ( '\\n'
or "\\n"
) and not slash-n.
When you write '/n'
, you should be getting a compiler warning about a multi-character character constant which is a non-portable piece of C.
Obviously, you could create a variable to hold the newline, but there's really no need; the string literal will be be fine. If you do, the correct notation would be:
const char newline[] = "\n";
You could write:
const char rather_odd[3] = { '/n' };
but...the braces are necessary, and the first character has a compiler-dependent value, and the other two characters are NUL '\\0'
. This uses more than the minimum necessary space, too; the newline
variable is a 2-byte array.
With your non-standard Write()
function, the correct syntax is probably:
Write(logs, "\n", 1);
This emits a single newline; if the previous string (the one in log
) was not itself terminated by a newline, you do not have a blank line in the file; you would have to write a second newline. You might even want to test that:
size_t len = strlen(log);
Write(logs, log, len);
len = (log[len-1] == '\n') ? 1 : 2;
Write(logs, "\n\n", len);
Note, too, that GCC will warn you about a global variable called log
(because the C standard reserves the name). Local variables are OK.
$ cat x.c
int x = '/n';
int log = 2;
$ gcc -c x.c
x.c:1:9: warning: multi-character character constant
x.c:2:5: warning: built-in function ‘log’ declared as non-function
$
I came across this problem recently while resurrecting some code last modified about 20 years ago.
(Testing with GCC 4.5.2 on MacOS X 10.6.6.)
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